There are many chemical applications, particularly analytical applications involving the use of liquid solvents, reactants or the like in which the presence of dissolved gases, and particularly air, is undesirable. A prime example of such an application relates to the fluids utilized in liquid chromatography where the presence of even small amounts of dissolved gases interferes with the accuracy and sensitivity of the results obtained. For example, air dissolved in the mobile phase can manifest itself in the form of bubbles which causes noise and drift as the mobile phase passes through the chromatographic detector. In situations where the dissolved gases are chemically active, unwanted modifications or deterioration in the chromatographic fluids can occur. Therefore, it is desirable to remove such species through a degassing process.
The degassing of liquid materials has been necessary to the success of many processes, and, consequently, various degassing methods have been employed for some time. Techniques have included heating or boiling the fluid to be degassed, exposing the material to a reduced pressure environment or vacuum, and using combination of heat and vacuum to reduce the amount of dissolved gases in the fluid. Ultrasonic energy has also been employed for such degassing purposes. As conventionally applied, however, these traditional techniques have generally fallen short of the desired degree of separation efficiency.
Vacuum degassing through a membrane apparatus has long been known, and generally utilizes a length of relatively small diameter, thin-walled, semi-permeable synthetic polymer resin material contained within an enclosed chamber held under a reduced pressure or vacuum in which the fluid to be degassed is caused to flow through the tube. One such apparatus is shown by Sims in U.S. Pat. No. 5,340,384, assigned to the same Assignee as in the present invention. Other such devices are shown in U.S. Pat. Nos. 5,183,486; 4,430,098; and 3,668,837.
While each of these devices employ a vacuum degassing approach, there remains a need, particularly with devices associated with liquid chromatography instruments, to provide a fluid degassing capability in fluid transfer lines operably coupling respective components of such chromatographic instruments. In conventional degassing systems, chromatographic fluids are routed into a distinct vacuum chamber for performing the degassing function thereat. In such a manner, a separate and distinct component must be incorporated into the chromatographic instrument assembly. Moreover, fluid transfer lines must be routed from respective fluid reservoirs to a distinct vacuum chamber prior to such fluid flow through the chromatographic instruments.
It is therefore a principle object of the present invention to provide fluid transfer lines as axially-disposed individual degassing chambers.
It is another object of the present invention to provide chromatographic fluid transfer lines which are operably coupled to vacuum sources so as to enable vacuum-type degassing upon the fluids passing therethrough.
It is a yet further object of the present invention to provide an elongated flow-through vacuum degassing apparatus having an outer impermeable tube and one or more semi-permeable inner tubes disposed coaxially therewithin, with fluids passing either through or around the inner semi-permeable tubes in a relatively low-pressure environment between the outer tube and the inner tubes so as to effect a vacuum degassing characteristic upon the semi-permeable inner tubes.
It is a still further object of the present invention to provide an elongated flow-through transfer line vacuum degassing apparatus having an outer tube and one or more inner tubes coaxially disposed therewithin, and wherein the inner tubes are formed from an amorphous perfluorinated copolymer material.
It is another object of the present invention to provide an elongated transfer line vacuum degassing apparatus that is sufficiently flexible so as to be readily manipulatable into desired configurations.